Diagnosis

Symbiotic stage. Single cells. Spherical in shape, measuring 12-14 /*m m diameter; surrounded by a five-layered theca consisting of a plasma membrane and four outer membranes; chloroplast single and peripheral; chloroplast lamellae formed from pairs of closely apposed thylakoids; girdle lamellae present; four ovoid pyrenoids suspended from the interior of the chloroplast by several projecting stalks arising from the chloroplast; pyrenoids surrounded by a cap of polysaccharide reserve; pyrenoid lamellae present, occurring in non-reduced form; large dinoflagellate nucleus and conspicuous nucleolus; small accumulation body; typical chromophycean or protozoan mitochondria situated to the interior of the chloroplast; trichocysts absent. Motile stage. Rotund, measuring 12-13 /an with a much reduced epicone formed in the shape of a beak and deflected to one side; chloroplast and pyrenoids as in symbiotic stage; pyrenoids situated in anterior end of hypocone; nucleus in posterior end of hypocone.